Diamox tablets and injection and Diamox SR capsules all contain the active ingredient acetazolamide, which is a type of medicine called a carbonic anhydrase inhibitor. Acetazolamide has a few different uses. Its main use is in treating glaucoma, which is a condition where the pressure inside the eyeball is too high.

What is Diamox used for?

Diamox tablets and injection are used for:

  • Open angle glaucoma.
  • Glaucoma caused by another disease of the eye (secondary glaucoma).
  • Lowering the pressure in the eye before surgery for closed angle glaucoma.
  • Excess fluid retention (oedema), for example caused by heart failure, pre-menstrual syndrome or other medicines.
  • Epilepsy.

Diamox tablets can also be used to prevent altitude sickness, though this is an unlicensed use of the medicine and should not be used as a subsitute for gradual acclimatisation to altitude.

Diamox SR capsules are only used for glaucoma.

How does Diamox work?

  • Diamox tablets and injection and Diamox SR capsules all contain the active ingredient acetazolamide, which is a type of medicine called a carbonic anhydrase inhibitor. Acetazolamide has a few different uses. Its main use is in treating glaucoma, which is a condition where the pressure inside the eyeball is too high.
  • The pressure within the eyeball is normally maintained by a continuous flow of liquid called aqueous humour through the eyeball. Aqueous humour is produced by a part of the eye called the ciliary body. If aqueous humour builds up inside the eyeball, this increases the pressure within the eyeball, known as intraocular pressure. This pressure needs to be reduced, as otherwise it can damage the optic nerve and impair vision.
  • Acetazolamide reduces the pressure in the eyeball by decreasing the production of aqueous humour. It does this by blocking the action of an enzyme in the body called carbonic anhydrase. Carbonic anhydrase is usually responsible for producing a salt called bicarbonate in the body. Bicarbonate is needed for the production of the aqueous humour. By decreasing the production of bicarbonate, acetazolamide decreases the production of aqueous humour.
  • Acetazolamide is sometimes used to help treat fluid retention. In this situation it works in the kidneys, where it increases the amount of bicarbonate that passes into the urine. Bicarbonate draws water alongside it from the kidneys into the urine. This results in a small increase in the amount of water being lost from the body, a process known as diuresis. Acetazolamide causes only minor water loss; it is a weak diuretic. It is normally used in combination with other different types of diuretics to relieve fluid retention.
  • Acetazolamide may also be used in the treatment of epilepsy. It is not fully understood how it works in this condition, though it is thought to stabilise the electrical activity of nerves.
  • The brain and nerves are made up of many nerve cells that communicate with each other through electrical signals. These signals must be carefully regulated for the brain and nerves to function properly. When abnormally rapid and repetitive electrical signals are released in the brain, the brain becomes over-stimulated and normal function is disturbed. This results in fits or seizures.
  • Certain chemicals must enter the nerve cells in order for electrical signals to be generated in the nerves. By decreasing the amount of bicarbonate produced in the body, acetazolamide alters the balance of chemicals in the blood. This may alter the amounts of chemicals that can enter the nerve cells. This in turn may help prevent the excessively rapid and repetitive firing of electrical signals and thus stabilise the electrical nerve activity in the brain.

How do I take Diamox?

  • Diamox tablets and Diamox SR capsules can be taken either with or without food.
  • Diamox SR capsules are sustained-release capsules that are designed to release the medicine slowly over the day. These capsules should be swallowed whole with a drink of water and not opened, chewed or crushed, as this would damage the sustained-release action.
  • The dose prescribed and how often the medicine needs to be taken depends on the condition being treated. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label your pharmacist has put on the packet of medicine.

Important information about Diamox

  • This medicine may cause drowsiness and various other side effects that could affect your ability to drive or operate machinery safely. You should not drive or operate machinery until you know how this medicine affects you and are sure that it won't affect your performance.
  • This medicine may cause skin rashes and you should consult your doctor if you develop a rash, skin peeling, itching, or other unexplained skin reaction while taking this medicine.
  • If you are having long-term treatment with this medicine it is recommended that you should have regular blood tests to monitor the levels of electrolytes (eg sodium and potassium) and the levels of blood cells in your blood. Consult your doctor immediately if you experience any of the following symptoms while taking this medicine, as they may indicate a problem with your blood cells: unexplained bruising or bleeding, purple spots, sore throat, mouth ulcers, high temperature (fever), feeling unusually tired or general illness.

Diamox should be used with caution in

  • Elderly people.
  • People with breathing difficulties such as emphysema.
  • People with decreased kidney or liver function.
  • People with a history of kidney stones.
  • People who have difficulty passing urine.
  • People who have unstable levels of electrolytes (salts such as sodium and potassium) in their blood.

Diamox should not be used in

  • People who are allergic to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole.
  • People with underactive adrenal glands (the glands that produce the body's natural steroid hormones).
  • People with low levels of potassium or sodium in their blood (hypokalaemia or hyponatraemia).
  • People with high levels of chloride in their blood (hyperchloraemic acidosis).
  • Severe kidney disease.
  • Severe liver disease.
  • Long-term use in a type of glaucoma called chronic non-congestive angle-closure glaucoma.
  • Pregnancy.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine for use during pregnancy has not been established. It should not be used in pregnancy, particularly during the first trimester. Seek further medical advice from your doctor.
  • This medicine may pass into breast milk in small amounts. It should be used with caution during breastfeeding and only if the benefit to the mother outweighs any potential risk to the nursing infant. Seek further medical advice from your doctor.

Possible side effects of Diamox

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

  • Pins and needles or tingling sensations, particularly in the hands or feet.
  • Decreased appetite.
  • Metallic taste in the mouth.
  • Increased production of urine (polyuria).
  • Flushing.
  • Headache.
  • Dizziness.
  • Thirst.
  • Fatigue.
  • Irritability.
  • Depression.
  • Decreased sex drive.
  • Drowsiness.
  • Confusion.
  • Disturbances of the gut such as nausea, vomiting, diarrhoea.
  • Problems with hearing.
  • Temporary short-sightedness.
  • Kidney stones.
  • Abnormal liver or kidney function.
  • Disturbances in the levels of electrolytes in your blood.
  • Disturbances in the normal numbers of blood cells in your blood.
  • Severe allergic skin reactions.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

If you think you have experienced a side effect from a medicine or vaccine you should check the patient information leaflet. This lists the known side effects and what to do if you get them. You can also get advice from your doctor, nurse or pharmacist. If they think it's necessary they'll report it for you.

How can Diamox affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

Acetazolamide may increase the blood levels of the following medicines and may therefore increase the risk of their side effects:

  • carbamazepine
  • ciclosporin
  • phenytoin
  • quinidine.

Acetazolamide can decrease the amount of lithium in the blood, making it less effective.

Acetazolamide can make the antibiotic methenamine less effective at treating urinary tract infections.

There may be an increase in side effects such as drowsiness, confusion, lethargy, hyperventilation and ringing in the ears when acetazolamide is taken with high doses of aspirin.

There may be an increased risk of osteomalacia and rickets if acetazolamide is used in combination with phenytoin, phenobarbital or primidone.

Acetazolamide can sometimes decrease the amount of potassium in the blood. If it is used in combination with any of the following medicines, which can also lower potassium in the blood, the risk of a low blood potassium level (hypokalaemia) may be increased:

  • beta2 sympathomimetics such as salbutamol, salmeterol
  • corticosteroids such as prednisolone, dexamethasone
  • diuretics such as furosemide, bendroflumethiazide
  • theophylline.

If you experience a low blood potassium level while taking this medicine this can increase the risk of side effects from the following medicines:

  • amiodarone
  • arsenic trioxide
  • digoxin
  • disopyramide
  • flecainide.